// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/socket/stream_socket.h"

#include "base/metrics/field_trial.h"
#include "base/metrics/histogram_macros.h"
#include "base/strings/string_number_conversions.h"
#include "base/values.h"

namespace net {

StreamSocket::UseHistory::UseHistory()
    : was_ever_connected_(false)
    , was_used_to_convey_data_(false)
    , omnibox_speculation_(false)
    , subresource_speculation_(false)
{
}

StreamSocket::UseHistory::~UseHistory()
{
    EmitPreconnectionHistograms();
}

void StreamSocket::UseHistory::Reset()
{
    EmitPreconnectionHistograms();
    was_ever_connected_ = false;
    was_used_to_convey_data_ = false;
    // omnibox_speculation_ and subresource_speculation_ values
    // are intentionally preserved.
}

void StreamSocket::UseHistory::set_was_ever_connected()
{
    DCHECK(!was_used_to_convey_data_);
    was_ever_connected_ = true;
}

void StreamSocket::UseHistory::set_was_used_to_convey_data()
{
    DCHECK(was_ever_connected_);
    was_used_to_convey_data_ = true;
}

void StreamSocket::UseHistory::set_subresource_speculation()
{
    DCHECK(was_ever_connected_);
    // TODO(jar): We should transition to marking a socket (or stream) at
    // construction time as being created for speculative reasons.  This current
    // approach of trying to track use of a socket to convey data can make
    // mistakes when other sockets (such as ones sitting in the pool for a long
    // time) are issued.  Unused sockets can be left over when a when a set of
    // connections to a host are made, and one is "unlucky" and takes so long to
    // complete a connection, that another socket is used, and recycled before a
    // second connection comes available.  Similarly, re-try connections can leave
    // an original (slow to connect socket) in the pool, and that can be issued
    // to a speculative requester. In any cases such old sockets will fail when an
    // attempt is made to used them!... and then it will look like a speculative
    // socket was discarded without any user!?!?!
    if (was_used_to_convey_data_)
        return;
    subresource_speculation_ = true;
}

void StreamSocket::UseHistory::set_omnibox_speculation()
{
    DCHECK(was_ever_connected_);
    if (was_used_to_convey_data_)
        return;
    omnibox_speculation_ = true;
}

bool StreamSocket::UseHistory::was_used_to_convey_data() const
{
    DCHECK(!was_used_to_convey_data_ || was_ever_connected_);
    return was_used_to_convey_data_;
}

void StreamSocket::UseHistory::EmitPreconnectionHistograms() const
{
    DCHECK(!subresource_speculation_ || !omnibox_speculation_);
    // 0 ==> non-speculative, never connected.
    // 1 ==> non-speculative never used (but connected).
    // 2 ==> non-speculative and used.
    // 3 ==> omnibox_speculative never connected.
    // 4 ==> omnibox_speculative never used (but connected).
    // 5 ==> omnibox_speculative and used.
    // 6 ==> subresource_speculative never connected.
    // 7 ==> subresource_speculative never used (but connected).
    // 8 ==> subresource_speculative and used.
    int result;
    if (was_used_to_convey_data_)
        result = 2;
    else if (was_ever_connected_)
        result = 1;
    else
        result = 0; // Never used, and not really connected.

    if (omnibox_speculation_)
        result += 3;
    else if (subresource_speculation_)
        result += 6;
    UMA_HISTOGRAM_ENUMERATION("Net.PreconnectUtilization2", result, 9);
}

} // namespace net
